The invention relates to an autostereoscopic method and a device for the three-dimensional representation of information according to a barrier-, lenticular-, prismatic masking-, or similar method using flat-panel displays (liquid crystal-, plasma-, electroluminescent- or other displays) for use in the computer and video technology, games and advertising, medical engineering, virtual reality applications, and other fields.
For the three-dimensional representation of information some autostereoscopic methods are already known, namely, among others, the barrier, lenticular, and prismatic masking methods (see, for example, S. Pastoor: 3D-Display-Technologie [3D display technology], Euroforum-Konferenz Display 1996, 17th and 18th Apr. 1996 in Nxc3xcrtingen/Germany; D. Ezra et al.: Blick in die dritte Dimension [Looking into the third dimension]. In: Fernseh- und Kinotechnik, vol. 50, no. 3/1996, pp. 79-82; DE 296 12 054 U1; R. Bxc3x6rner: Autostereoscopic 3D-imaging by front and rear projection and on flat panel displays. In: Displays, vol. 14, no. 1, 1993, pp. 39-46; Autostereoscopic 3-D Image Display Device. In: IBM TDB, Vol. 37, no. 8, August 1994, pp. 463-465).
Using these methods, two images of a stereoscopic pair are simultaneously generated, one for the right eye and another for the left eye, and represented in a number of horizontally adjacent vertical columns, one image in columns for the right eye (in the following, right columns) and the other in columns for the left eye (in the following, left columns). The right columns and left columns alternately follow each other. Each two successive columns, one right and one left, form a pair of columns. From the two plain, fringe-like images of the pair the observer gains, due to his/her vision, a three-dimensional image impression.
The display by which the images of the pair are generated contains a number of pixels that are arranged as a matrix and vertically below each other compose the columns for the images. On usual direct-sight color displays each pixel technically consists of three colored subpixels for the three primaries red (R), green (G) and blue (B). On other displays the number of the colored subpixels is increased, for example, there is a second B-colored subpixel provided for each pixel. In a generalized mode, each pixel consists of n colored subpixels. By superpositioning the color contents of each n colored subpixels of the pixels image points develop on the display the raster of which corresponds to the matrix of the pixels. By each pixel column an image column is formed on the display from one of the two images of the pair. Each column has one image point per line. The colored subpixels are usually arranged in the pixels horizontally side by side, and repeat periodically on the lines, e.g. RGB, RGB, . . . or BRGB, BRGB, . . . . Sequence and number n of the colored subpixels per period are determined by the design of the individual display. A color filter is assigned to each colored subpixel. Each colored subpixel is addressed corresponding with the appropriate value of intensity. The intensity values are given for each image by programming means.
The information in the right and left columns are assigned to the right and the left eye, respectively, using optical means, e.g. imaged in them. In the lenticular system each pair of columns is assigned a cylindrical lens. In the barrier method the columns are covered by line-shaped barriers such that the left eye can only see the left columns and the right eye can only see the right columns while the other columns are shaded in each case. In the prismatic masking method, prisms are arranged in front of the columns in a separation and a field lens mask, or in a combined separation/field lens mask respectively. The bundles of rays emerging from the right and left columns are horizontally separated using the prisms of the separation mask and spread by direction by about 6xc2x0 corresponding with the spacing of the eyes whereby the right and left ray bundles each run parallel. The prisms of the field lens mask focus the right ray bundles onto the right eye and the left ray bundles onto the left eye. With both masks arranged behind each other, or with the combined separation/field lens mask respectively, two cones of light develop emerging from the display in the apeces of which the eyes of the observer are.
From this, observer positions ensue in that the right eye sees only the right columns and the left eye sees only the left columns. These observer positions repeat periodically when the observer moves laterally in front of the display. In these ideal observer positions the columns are assigned to the observer""s eyes correct and in full width. For a small lateral displacement the match of columns and optical means reduces relative to the observer position. The right eye receives, for example, just 80% of the information of the right picture but 20% of the left. Cross-talk interference arises between the two image channels as soon as the observer moves. The stereo contrast reduces. The proportions of wrong information rise when the observer continues to move laterally until a total reverse of the information takes place, that is, information for the right eye is assigned to the left and vice versa. The observer sees a pseudoscopic picture. When the lateral movement is continued, the laterally correct information contents grow up reaching 100% correct assignment again.
Already known is to monitor the lateral position of the observer relative to the screen. For example, the position of the head and thus of the eyes relative to the screen can be determined using a commercial infrared camera (e.g., DynaSight of Origin Instruments Corp., Grand Prairie, Tex., USA).
In the lenticular system the lens mask, and in the barrier method the barrier grating are mechanically followed. In other solutions the light of the light sources is laterally followed, or the screen is turned on a vertical axis. Generally, the pictures of the stereoscopic pair or the optical means to see the pictures, respectively, are followed to the lateral movement of the observer.
Also already known is the electronic switching of the picture information in those positions where the observer gains a pseudoscopic image.
The mechanical tracking devices require additional drive mechanisms, with an additional effort in manufacture, maintenance and space. Furthermore, they are relatively slow compared to electronic switching times. Problems increase with growing travel distance.
The electronic switching of the picture information can be carried out by programmes, that is, without any additional effort in hardware. The observer, however, must still remain in the ideal seating positions; only the number of them doubles. In the positions between the ideal ones, there is still cross-talk interference with resulting badly reduced image quality.
This is particularly significant with today""s color displays. Between the ideal positions the observer sees, for example, instead of the red contents corresponding to the right image, the red contents corresponding to the left image and these form combined with the still correct green and blue color contents significantly disturbed stereo images. In this example, the stereo images for the green and blue color contents are correct. But as fas as the red color content is concerned, an inverse stereo image is obtained with the appropriate pseudoscopic effect.
The lenticular system amplifies this effect in a specific way. In order to cope with this, the display was turned by 90xc2x0. By this, the colored subpixels of each pixel are arranged below each other so that the original color values are proportionally maintained when the observer moves. This turn, however, requires a new design of the display.
It is the objective of the invention, when using a flat panel display whose pixels have n colored subpixels each arranged horizontally side by side and periodically following each other in a line, to track the images of a stereoscopic pair relative to lateral changes of the observer position such that the high stereoscopic image quality existing in the ideal observer positions is largely maintained.
According to the invention the problem is solved in that the image points are laterally shifted proportionally to the movement of the observer by shifting, for each colored subpixel, the intensities of the colored subpixels to colored subpixels horizontally adjacent on the display.
The method can be successfully realized, if in a first version, as already known, n colored subpixels per image point are available. The number of the ideal observer positions is raised to six per period of the ideal observer positions without image tracking. The stereoscopic cross-talk interference between the ideal positions is limited to a very low level by shifting the intensities, preferably for each colored subpixel in intermediate steps.
In another embodiment of this first version, a similar effect is achieved due to the fact that the programmed shifting, for each colored subpixel, of the image contents on the non-moving screen according to the invention is combined with the already known lateral shifting of the display or the light of the light sources or the optical means (e.g., of a barrier grating or of cylindrical lenses). Hereby the travel distance can be kept very small because the compensation must only include the full width of a colored subpixel. By this ideal image quality is achieved in each observer position. The method according to the invention becomes especially useful when, in a second version, n+1 adjacent colored subpixels per image point are addressed whereby the intensities of the two equally colored subpixels located at the borders of each image point are identical and preferably correspond to the intensity of this color in the image point, and the horizontal width of the visible part of an image point corresponds to n colored subpixel widths.
Considering a usual color display manufactured up to now, with n adjacent colored subpixels per pixel, the image points, or image columns, respectively, each are by one colored subpixel width wider than the pixels, or pixel columns, respectively.
In a preferable embodiment using a usual display with three colored subpixels in the colors RED (R), GREEN (G) and BLUE (B) periodically following each other in a line, for each image point four colored subpixels are addressed. On the display line the colored subpixels with the sequences RGBR, GBRG, BRGB, etc. form the image points.
In an ideal position in front of the screen the observer sees with the right and left eye, respectively, of the n+1 colored subpixels of each image point the two colored subpixels on the border of this image point half-width and the nxe2x88x921 colored subpixels in between full-width. When laterally changing his/her position little, he/she sees of one of the two border subpixels a correspondingly smaller portion, e.g., only 20% of the colored subpixel width, but 80% of the width of the other border subpixel. As a sum, the intensity of the color content of the border subpixels is fully maintained. The observer continues to see a stereoscopicallyxe2x80x94as well as laterallyxe2x80x94and color-correct stereo image.
With growing distance of the observer from the display, the color content of the border subpixels reduces. The reduction, however, is usually only a few percent so that the image impression hardly deteriorates.
Thus the arrangement according to the invention xe2x80x9ctoleratesxe2x80x9d small lateral movements as well as greater changes of the distance of the observer from the display without noticeable worsening of the image quality.
On longer lateral movements of the observer the image points in the lines are, according to the invention, shifted by one or several colored subpixel widths and the intensity levels belonging to the image points, of the colors in the colored subpixels are assigned to the adjacent n+1 colored subpixels in the line, which are at the new position of the image point. The magnitude of the lateral shifting of the image points approximately corresponds to the lateral positional change of the observer. While the pixels and colored subpixels are bound to their positions on the display, the image points shift along the display line corresponding to the lateral movement of the observer. In conjunction with the xe2x80x9ctolerancexe2x80x9d of the system (theoretically, a displacement of one colored subpixel width maximum is allowed) the observer continues to see the image in practically consistently high quality. During the movement of the observer the same information can be shown. But the information can also change with lateral displacement of the observer. For example, the observer sees more of the right or of the left side of an object.
For an embodiment of the device preferably designed with a barrier grating the width of the bars of the barrier grating is greater than the width of the slits between the bars of the barrier grating, whereby the bars in the path of the rays to the eyes of the observer cover n+1 widths of colored subpixels and the slits between the bars are open for n widths of colored subpixels each.
It is shown by the subclaims and examples of embodiment that it is equally possible with the features according to the invention to build a prism or lenticular mask arrangement.
The invention is represented in the FIGS. 1 to 4 for the first version (n colored subpixels per image point), and in the remaining figures for the second version (n+1 colored subpixels per image point). For both versions, the different embodiments are first explained by an arrangement for a barrier method. The last two figures show the completely unproblematic transfer to arrangements for a lenticular or a prismatic masking method. Always by means of a horizontal section, the drawings show the intensity values at the colored subpixels for different observer positions: